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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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12345678910111213141516171819202122232425262728293031323334353637383940// SPDX-License-Identifier: GPL-2.0#include <linux/export.h>#include <linux/bug.h>#include <linux/bitmap.h>
/** * memweight - count the total number of bits set in memory area * @ptr: pointer to the start of the area * @bytes: the size of the area */size_t memweight(const void *ptr, size_t bytes){ size_t ret = 0; size_t longs; const unsigned char *bitmap = ptr;
for (; bytes > 0 && ((unsigned long)bitmap) % sizeof(long); bytes--, bitmap++) ret += hweight8(*bitmap);
longs = bytes / sizeof(long); if (longs) { BUG_ON(longs >= INT_MAX / BITS_PER_LONG); ret += bitmap_weight((unsigned long *)bitmap, longs * BITS_PER_LONG); bytes -= longs * sizeof(long); bitmap += longs * sizeof(long); } /* * The reason that this last loop is distinct from the preceding * bitmap_weight() call is to compute 1-bits in the last region smaller * than sizeof(long) properly on big-endian systems. */ for (; bytes > 0; bytes--, bitmap++) ret += hweight8(*bitmap);
return ret;}EXPORT_SYMBOL(memweight);